Button cell having winding electrode and method for the production thereof

ABSTRACT

A button cell includes a housing having a metal cell cup and a metal cell top. The button cell is a secondary lithium ion cell. An electrode winding disposed within the housing is formed from a multi-layer assembly that is wound in a spiral shape about an axis. The multi-layer assembly including a positive electrode, a negative electrode, and a separator disposed between the electrodes. A first conductor is provided that includes a strip-shaped portion that lies flat between a first end side of the electrode winding and a first of the cell cup and cell top. A second conductor is provided that includes a strip-shaped second portion that lies flat between a second end side of the electrode winding and a second of the cell cup and cell top. The first conductor and the second conductor are metal foils.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is a divisional of U.S. application Ser. No.15/699,435, filed Sep. 8, 2017, which is a divisional application ofU.S. application Ser. No. 13/378,117 filed Dec. 14, 2011, which is a §371 of International Application No. PCT/EP2010/058637, with aninternational filing date of Jun. 18, 2010 (WO 2010/146154 A2, publishedDec. 23, 2010), which is based on German Patent Application Nos. 10 2009030 359.6, filed Jun. 18, 2009, and 10 2009 060 800.1, filed Dec. 31,2009, all of which applications are hereby incorporated by referenceherein.

FIELD

This disclosure relates to button cells having a housing consisting oftwo metal housing halves, which contains a wound electrode separatorassembly, and to a method for its production.

BACKGROUND

Button cells conventionally comprise a housing consisting of two housinghalves: a cell cup and a cell top. These may, for example, be producedas stamped parts from nickel-plated deep-drawn sheet metal. Usually, thecell cup is positively poled and the housing top negatively poled. Thehousing may contain a very wide variety of electrochemical systems, forexample, zinc/MnO₂, primary and secondary lithium systems, or secondarysystems such as nickel/cadmium or nickel/metal hydride.

The liquid-tight closure of button cells is conventionally carried outby crimping the edge of the cell cup over the edge of the cell top, incombination with a plastic ring which is arranged between the cell cupand the cell top and is used simultaneously as a sealing element and forelectrical insulation of the cell cup and the cell top. Such buttoncells are described, for example, in DE 31 13 309.

As an alternative, however, it is also possible to manufacture buttoncells in which the cell cup and the cell top are held together in theaxial direction exclusively by a force-fit connection, and whichcorrespondingly do not have a crimped cup edge. Such button cells and amethod for their production are described in DE 10 2009 017 514.8.Regardless of the various advantages which such button cells withoutcrimping may present, they nevertheless cannot withstand such highstresses in the axial direction as comparable button cells with acrimped cup edge, especially as regards axial mechanical loads whichoriginate from inside the button cell. For example, the electrodes ofrechargeable lithium ion systems are constantly subjected to volumechanges during charging and discharging processes. In button cellswithout crimping, the axial forces occurring in this case can naturallycause leaks more easily compared with button cells with crimping.

A solution to this problem may be found in DE 10 2009 030 359.6 and DE10 2009 008 859.8. Inter alia, references may be found therein to buttoncells comprising a housing having a plane bottom region and a plane topregion parallel thereto, an assembly consisting of flat electrode layersand separator layers in the form of a preferably spiral-shaped electrodewinding being arranged in the housing in such a way that the end sidesof the winding face in the direction of the plane bottom region and theplane top region. The electrode layers of the winding are thus orientedessentially orthogonally to the plane bottom and top regions of thehousing. As a result, radial forces such as occur during theaforementioned charging and discharging processes of lithium ion systemscan in principle be absorbed better than in of conventional lithium ionbutton cells, in which electrode layers are arranged stacked in parallelalignment with the plane bottom and top regions.

Windings consisting of flat electrode layers and separator layers can beproduced quite straightforwardly using known methods (see, for example,DE 36 38 793) by the electrodes being applied, in particular laminated,particularly in the form of strips, flat onto a separator provided as anendless band. The assembly consisting of the electrodes and separatorsis generally wound on a so-called “winding mandrel.” After the windinghas been removed from the winding mandrel, an axial cavity is left atthe center of the winding, the effect of which is that the winding maypossibly expand into this cavity. This, however, can sometimes lead toproblems in the electrical contact of the electrodes with the metalhousing halves.

It could therefore be helpful to provide a button cell in which theaforementioned problems do not occur, or only occur to a greatly reducedextent.

SUMMARY

The present invention provides a button cell having a housing. Thehousing includes a metal cell cup and a metal cell top. The metal cellcup has a cell cup plane region and the metal cell top has a cell topplane region extending substantially parallel to the cell cup planeregion. An electrode winding is disposed within the housing, theelectrode winding having a first end side, a second end side, and anouter side. The first end side and the second end side extendsubstantially parallel to the cell cup plane region and the cell topplane region. The electrode winding is formed from a multi-layerassembly that is wound in a spiral shape about an axis. The multi-layerassembly includes a positive electrode formed from a first currentcollector coated with a first electrode material, a negative electrodeformed from a second current collector coated with a second electrodematerial, and a separator disposed between the positive electrode andthe negative electrode. The button cell further includes a firstconductor including a first portion extending substantiallyperpendicular to the first end side of the electrode winding, astrip-shaped second portion, and a bend connecting the first portion tothe second portion. The strip-shaped second portion of the firstconductor lies flat between (i) the first end side of the electrodewinding and (ii) a first of the cell cup plane region or the cell topplane region. The strip-shaped second portion of the first conductor hasa length that is less than a diameter of the first end side of theelectrode winding. The button cell additionally includes a secondconductor including a first portion extending substantiallyperpendicular to the second end side of the electrode winding, astrip-shaped second portion, and a bend connecting the first portion tothe second portion. The strip-shaped second portion of the secondconductor lies flat between (i) the second end side of the electrodewinding and (ii) a second of the cell cup plane region or the cell topplane region. The strip-shaped second portion of the second conductorhas a length that is less than a diameter of the second end side of theelectrode winding. The first conductor and the second conductor,including the respective first portions, second portions, and bendsthereof, are metal foils. The button cell is a secondary lithium ioncell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B schematically show a cross section of a preferredexample of a button cell 100.

FIGS. 2A to 2C schematically show selected assembly steps of the buttoncell of FIG. 1.

FIGS. 3A and 3B schematically show selected views of windings of thebutton cell.

FIGS. 4A and 4B schematically show two different welds.

FIG. 5 shows microphotographs of a weld from top and cross-sectionalviews.

DETAILED DESCRIPTION

My button cell always comprises two metal housing halves separated fromone another by an electrically insulating seal and forming a housinghaving a plane bottom region and a plane top region parallel thereto. Asmentioned above, the two housing halves are generally a so-called“housing cup” and a “housing top.” In particular, nickel-plated steel orsheet metal are preferred as the material for the housing halves.Trimetals, in particular, are furthermore suitable as the metallicmaterial, for example, ones comprising the sequence nickel, steel (orstainless steel) and copper (in which case the nickel layer preferablyforms the outer side of the button cell housing and the copper layerpreferably forms the inner side).

As the seal, it is, for example, possible to use an injection-moldedseal or a film seal. The latter are described, for example, in DE 196 47593.

At least one positive electrode and at least one negative electrode arearranged inside the housing, specifically each in the form of flatelectrode layers. The electrodes are preferably connected to one anotherby at least one flat separator. The electrodes are preferably laminatedor adhesively bonded onto this separator. The electrodes and theseparator generally each have a thickness only in the μm range. A porousplastic film is generally used as the separator.

This assembly is provided in the form of a winding, particularly in theform of a spiral-shaped winding, in the housing of a button cell, thewinding being arranged such that its end sides face in the direction ofthe plane bottom region and the plane top region of the housing. Fullreference is hereby made to the description of such windings, and buttoncells comprising such windings, in DE 10 2009 030 359.6 and DE 10 2009008 859.8 already mentioned above. All the preferred forms described inthose applications are also intended to apply for the button celldescribed here and the electrode winding described here.

Besides the housing halves and the electrode separator assembly, mybutton cell always also comprises metal conductors which electricallyconnect the at least one positive electrode and/or the at least onenegative electrode respectively to one of the housing halves. Theconductor or conductors connected to the at least one positive electrodepreferably consist of aluminum. The conductors connected to the at leastone negative electrode preferably consist of nickel or copper.

On the electrode side, the conductors are preferably connected tocurrent collectors. The latter are generally metal foils or meshesconventionally coated on both sides with active electrode material.These current collectors preferably consist of aluminum on the side ofthe positive electrode, and preferably nickel or copper on the side ofthe negative electrode. The foils or meshes have, in particular,thicknesses of between 1 μm and 100 μm. The connecting of the conductorsto the current collectors is preferably carried out by welding.

Particularly in respect of preferred forms of the electrode separatorassembly arranged in my button cell, reference is made to DE 10 2009 030359.6 and DE 10 2009 008 859.8. These disclose in particular preferredlayer sequences and layer thicknesses for electrodes and separators, forexample, an assembly comprising the layer sequence:

-   -   negative electrode/separator/positive electrode/separator or    -   positive electrode/separator/negative electrode/separator.

Assemblies comprising the layer sequences:

-   -   negative electrode/separator/positive        electrode/separator/negative electrode or    -   positive electrode/separator/negative        electrode/separator/positive electrode may also be preferred.        The assembly therefore comprises more than one positive        electrode and/or more than one negative electrode.

Particularly preferably, at least one of the electrodes of a button cellis a lithium intercalation electrode. The button cell is preferably alithium ion battery, in particular a secondary lithium ion battery.

My button cell is distinguished particularly in that at least one of theconductors is welded to the respective housing half, preferably both theconductor connected to the at least one positive electrode and theconductor connected to the at least one negative electrode.

As has already been mentioned above, particularly in lithium ion buttoncells, the electrodes are subject to volume changes during acharging-discharging cycle, as a result of which contact problems mayarise between the conductors and the housing halves. Such contactproblems no longer apply when the conductors are welded to therespective housing halves.

Particularly preferably, the conductor or conductors are welded onto theinner side of the housing in the plane bottom region or the plane topregion, respectively, of the housing. For this purpose, according toconventional methods the welding process must be carried out before thehousing is assembled, which is very difficult to achieve in terms ofproduction technology. Welded connections have therefore been regardedas highly disadvantageous for bonding the conductors to the inner sideof the housing halves. By virtue of my method as described in moredetail below, however, a solution can be provided which also has greatadvantages in terms of production technology.

By the welding, the at least one positive electrode and/or the at leastone negative electrode are thus connected by one or more conductorsdirectly to the plane bottom region or to the plane top region of thehousing of a button cell, the housing top generally being polednegatively and the housing cup positively.

The button cell is preferably a conventional button cell having acircular plane bottom region and a circular plane top region. In somecases, the button cell may nevertheless have an oval configuration. Itis, however, important that the ratio of height to diameter ispreferably always less than 1. Particularly preferably, it is 0.1 to0.9, in particular 0.15 to 0.7. The height is intended to mean theshortest distance between the plane bottom region and the plane topregion parallel thereto. The diameter means the maximum distance betweentwo points on the lateral region of the button cell.

Preferably, the conductors of a button cell are flat conductors, inparticular metal foils, particularly preferably rectangular, strip- orband-shaped metal foils. The foils preferably have thicknesses of 5 μmto 100 μm.

The conductors are preferably separate components bonded, in particularwelded, to the electrodes, in particular to the current collectors inthe electrodes. As an alternative, however, the conductors may also beuncoated sections of a current collector (sections which are free ofactive electrode material), in particular the uncoated ends of such acurrent collector. By bending these uncoated sections, in particularthese uncoated ends, for example, through 90°, these ends can beconnected to the bottom or top region of a button cell. There, theconnecting is preferably carried out by welding.

Preferably, at least one subsection of the conductor or conductors bearsflat on the inner side of the housing half or halves in the bottomand/or top region of the housing, in particular when the conductors areflat conductors such as foils. Such conductors may form a flat layerbetween the inner side of the housing halves and an end side of theelectrode winding, and therefore a large-area electrical contact withthe housing.

Since in principle both positive and negative electrodes may be exposedon the end sides of the electrode winding, however, it is necessary toavoid a short circuit between the electrodes. Particularly preferably,my button cell therefore comprises at least one separate insulatingmeans which prevents direct electrical contact between the end sides ofthe winding and the conductors, in particular a subsection of theconductor or conductors which bears flat on the inner side of thehousing halves. Such an insulating means may, for example, be a film,for example, a plastic adhesive film, by which the side of the conductoror conductors remote from the inner side of the button cell housing iscovered.

The electrode winding of a button cell may be produced by known methods,for example, the method described in DE 36 38 793, according to whichelectrodes and separators are wound on a winding mandrel. After thewinding has been removed from the winding mandrel, there may be an axialcavity at the center of the winding, preferably an essentiallycylindrical axial cavity. In the housing of my button cell, such acavity is delimited laterally by the winding and on the end sides by thebottom or top region of the housing, respectively, or at least by asubregion thereof. Particularly preferably, the at least one conductoris welded to one housing half or the housing halves in one of thesesubregions.

The axial cavity may optionally contain a winding core, which canprevent the winding from expanding uncontrolledly into the cavity.

The button cell is in particular a button cell without crimping, as isdescribed in DE 10 2009 017 514.8. Accordingly, there is preferably anexclusively force-fit connection between the housing halves. The but-toncell thus does not have a crimped cup edge, as is always the case withbutton cells known from the prior art. The button cell is closed withoutcrimping. The content of DE 10 2009 017 514.8 is also fully incorporatedherein by reference. All the preferred forms described in thatapplication is also intended to apply for the button cell described hereand its housing.

As already mentioned above, welding of conductors to the inner side ofbutton cell housings is very elaborate in terms of productiontechnology. I overcome this problem with my method of producing buttoncells, which always comprises at least the following steps:

-   -   (a) providing a first and a second metal housing half        (preferably a cell cup, and a cell top),    -   (b) placing an electrode separator assembly comprising a        positive electrode and a negative electrode in one of the        housing halves (preferably into the cell top), a metal conductor        being bonded to at least one of the electrodes (preferably to        all the electrodes),    -   (c) assembling the two housing halves (preferably by inserting        the cell top into the cell cup), optionally with the provision        of separate steps for sealing the housing (for example, fitting        a seal) and    -   (d) welding at least one of the conductors to the inner side of        one of the metal housing halves.

The components used in the method such as the housing halves, theconductors and the electrode separator assembly, have already beendescribed above. Reference is hereby made to the corresponding remarks.

The method is distinguished in particular in that step (d) is carriedout after step (c). This means that the at least one conductor is weldedto the inner side of the housing when the housing is closed. The weldingmust correspondingly be carried out from the outside through the housingwall of one or both housing halves.

Accordingly, I provide button cells which have weld beads and/or weldspots that pass through the housing, in particular starting from itsouter side.

Particularly preferably, the conductor or conductors and the button cellhousing are connected to one another by one or more spot-like and/orlinear welded connections.

Welding the conductors and the housing is preferably carried out by alaser. Its operating parameters must be adapted as accurately aspossible to the thickness of the housing. The power may, for example, bemodulated by varying the pulse frequency. Lastly, the laser shouldmerely ensure welding of the housing and conductors while othercomponents such as the electrode winding should as far as possible notbe damaged.

Suitable lasers are, for example, commercially available fiber lasers,i.e., solid-state lasers, in which the doped core of a glass fiber formsthe active medium. The most common dopant for the laser-active fibercore is erbium. For high-power applications as in the present case,however, ytterbium and neodymium are more preferred.

Irrespective of the fact that such lasers can be adapted very finely tothe respective housing thickness and conductor dimension, it isnevertheless possible that in certain cases the intensity of the laserwill be selected to be too strong and the laser will penetrate throughthe housing wall and the conductor. For this reason, welding theconductors to the housing is particularly preferably carried out in thesubregion of the bottom or top region, which delimits the axial cavityat the center of the winding on the end side. If a laser beam penetratesthrough the housing in this region, the winding cannot be damaged.Instead, the laser beam will be absorbed by the housing half lyingopposite or by a winding core optionally arranged inside the cavity.

If possible, the conductors to be welded should bear as flatly aspossible on the inner side of the housing. This may, for example, beensured by fixing the conductors flat by an adhesive tape onto or at theend sides of an electrode winding, before the latter is inserted intothe housing.

The aforementioned advantages, and further advantages thereof, are inparticular also revealed by the description which now follows of thedrawings. In this context, the individual features may be implementedseparately or in combination with one another. The examples describedmerely serve for explanation and better understanding, and are in no wayto be interpreted as restrictive.

Button cell 100 comprises two metal housing halves: a metal cup part 101and a metal top part 102. With a seal 103 lying between them, the twoparts are connected together in a leaktight fashion. Together, they forma housing having a plane bottom region 104 and a plane top region 105parallel thereto. In the functional state, these two plane regions 104and 105 form the poles of the button cell 100, from which current can bedrawn by a load. The cell top 102 is inserted into the cell cup 101 sothat the lateral surface regions of the cell top and the cell cupoverlap, the internal radius of the cell cup 101 in the overlap region106 being essentially constant in the direction of the rim 107. The edgeof the cell 101 is thus not crimped. The button cell 100 is therefore anuncrimped button cell.

An assembly 108 of strip-shaped electrodes and strip-shaped separatorsis arranged inside the electrode. The assembly 108 is provided in theform of a spiral-shaped winding, the end sides of which face in thedirection of the plane bottom region 104 and the plane top region 105parallel thereto. The assembly is wound on the winding core 109 at thecenter of the button cell 100. The winding core is a hollow plasticcylinder, which partially fills an axial cavity at the center of thewinding. The cavity itself is delimited laterally by the winding andupward and downward by corresponding circular sections of the plane cupand top regions of the button cell housing. Metal foils 110 and 111,which act as conductors and are connected to the electrodes, bear flaton these regions. These conductors are shielded from the end sides ofthe winding by the insulating elements 112 and 113. The latter are thinplastic films. The wall thickness of the housing in the region of theplane bottom or top region is generally 30 μm to 400 μm. The thicknessof the metal foils 110 and 111 acting as conductors generally lies 5 μmto 100 μm.

Welding of the metal foils 110 and 111, acting as conductors, to therespective housing half, which is preferably done by the schematicallyrepresented laser 114, is preferably carried out in that subregion ofthe bottom region or of the top region of the button cell housing whichdelimits the axial cavity at the center of the winding on the end side.This creates a weld bead 115 which passes fully through the housing ofthe button cell 100 from the outside inward, and by which the internallylying metal foils 110 and 111 acting as conductors are firmly connectedto the inner side of the housing. This can be seen clearly in the detailenlargement (FIG. 1B).

FIG. 2A to FIG. 2C represent some important steps in the production ofan electrode winding, which is suitable in particular for button cells(for example, as represented in FIG. 1). Thus, FIG. 2A shows segmentedcollector foils 201 and 202 coated with active electrode material, towhich conductor strips 203 and 204 offset at an angle of 90° areattached by welding. The conductor 204 on the anode side consists ofnickel or copper, and the conductor 203 on the cathode side of aluminum.The conductors 203 and 204 are respectively applied in a material-freeregion (205, 206) of the collector foils 201 and 202. Elsewhere, theyare coated with active material on both sides. The connection betweenthe collector foils 201 and 202 and the conductors may, for example, beproduced by welding in the region 211.

FIG. 2B and FIG. 2C represent the way in which the rear sides of theconductors 203 and 204 are adhesively bonded using an insulating tape207 and 208 (for example, made of KAPTON or polypropylene) (Step 2).This insulating tape is subsequently intended to function as aninsulating element, which is meant to prevent direct electrical contactbetween the conductors 203 and 204 and the end sides of the electrodewinding which is to be produced. The conductors 203 and 204 are fixed onthe front in a further step (Step 3) with further adhesive strips 209and 210. The region 211 is bonded over in this case.

The conductor position in a winding of electrode foils obtainedaccording to FIG. 2A to FIG. 2C can be seen clearly in FIG. 3A. Twodifferent perspective representations of the same winding are shown(left and right). The conductor 301 (which corresponds to the conductor204 in FIG. 2) and the conductor 302 (which corresponds to the conductor203 in FIG. 2) are themselves aligned axially at a 90° angle to thewinding direction and by folding down by 90° bear flat on the end sides303 and 304 of the electrode winding. The insulating elements 305 and306 (which correspond to the insulating tapes 207 and 208 in FIG. 2)prevent direct electrical contact between the conductors 301 and 302 andthe end sides 303 and 304 of the electrode winding represented. Theouter side of the winding is protected by the insulating film 307.Ideally, the conductors 301 and 302 overlap with the openings of theaxial cavity 308 on the end sides so that welding to the button cellhousing can be carried out in this region. This can be seen clearly inFIG. 3B, as can the winding core 309 which fills the axial cavity 308.

FIGS. 4A and 4B show possible welding variants. For example, it ispossible to configure the weld bead as a minus sign 401 or a plus sign402 (see the respective enlarged representations on the right) so as toindicate the polarity of the respective housing half at the same time.The plus sign 402 is preferably applied on the lower side 404 of abutton cell, and the minus sign on the upper side 403.

FIG. 5 shows an enlarged representation of a cross section through ahousing half 500 of a button cell. The stainless steel cup wall 501, thealuminum conductor 502 bearing flat underneath and an insulating tape503 of KAPTON film arranged below can be seen. The weld beads 504 and505, which extend from the outer side of the housing inward as far asthe insulating tape 503 of KAPTON film can be seen clearly. The top leftimage is a plan view of the cutaway plane bottom region of the housinghalf 500. The housing half 500 and the conductor 502 have been weldedusing an ytterbium-doped fiber laser of the YLR-400-AC type(manufacturing company IPG Photonics Corporation, USA). The intensity ofthe laser was in this case adjusted so that the insulating tape 503 wasnot penetrated.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and descriptionare to be considered illustrative or exemplary and not restrictive. Itwill be understood that changes and modifications may be made by thoseof ordinary skill within the scope of the following claims. Inparticular, the present invention covers further embodiments with anycombination of features from different embodiments described above andbelow. Additionally, statements made herein characterizing the inventionrefer to an embodiment of the invention and not necessarily allembodiments.

The terms used in the claims should be construed to have the broadestreasonable interpretation consistent with the foregoing description. Forexample, the use of the article “a” or “the” in introducing an elementshould not be interpreted as being exclusive of a plurality of elements.Likewise, the recitation of “or” should be interpreted as beinginclusive, such that the recitation of “A or B” is not exclusive of “Aand B,” unless it is clear from the context or the foregoing descriptionthat only one of A and B is intended. Further, the recitation of “atleast one of A, B and C” should be interpreted as one or more of a groupof elements consisting of A, B and C, and should not be interpreted asrequiring at least one of each of the listed elements A, B and C,regardless of whether A, B and C are related as categories or otherwise.Moreover, the recitation of “A, B and/or C” or “at least one of A, B orC” should be interpreted as including any singular entity from thelisted elements, e.g., A, any subset from the listed elements, e.g., Aand B, or the entire list of elements A, B and C.

What is claimed is:
 1. A button cell, comprising: a housing, the housingincluding: a metal cell cup, the metal cell cup having a cell cup planeregion, and a metal cell top, the metal cell top having a cell top planeregion extending substantially parallel to the cell cup plane region; anelectrode winding disposed within the housing, the electrode windinghaving a first end side, a second end side, and an outer side, the firstend side and the second end side extending substantially parallel to thecell cup plane region and the cell top plane region, the electrodewinding being formed from a multi-layer assembly that is wound in aspiral shape about an axis, the multi-layer assembly including: apositive electrode formed from a first current collector coated with afirst electrode material, a negative electrode formed from a secondcurrent collector coated with a second electrode material, and aseparator disposed between the positive electrode and the negativeelectrode; and a first conductor including a first portion extendingsubstantially perpendicular to the first end side of the electrodewinding, a strip-shaped second portion, and a bend connecting the firstportion to the second portion, wherein the strip-shaped second portionof the first conductor lies flat between (i) the first end side of theelectrode winding and (ii) a first of the cell cup plane region or thecell top plane region, and wherein the strip-shaped second portion ofthe first conductor has a length that is less than a diameter of thefirst end side of the electrode winding; a second conductor including afirst portion extending substantially perpendicular to the second endside of the electrode winding, a strip-shaped second portion, and a bendconnecting the first portion to the second portion, wherein thestrip-shaped second portion of the second conductor lies flat between(i) the second end side of the electrode winding and (ii) a second ofthe cell cup plane region or the cell top plane region, and wherein thestrip-shaped second portion of the second conductor has a length that isless than a diameter of the second end side of the electrode winding;wherein the first conductor and the second conductor, including therespective first portions, second portions, and bends thereof, are metalfoils, wherein the button cell is a secondary lithium ion cell.
 2. Thebutton cell as claimed in claim 1, wherein the second portion of thefirst conductor is welded to the first of the cell cup plane region orthe cell top plane region.
 3. The button cell as claimed in claim 2,wherein the second portion of the second conductor is welded to thesecond of the cell cup plane region or the cell top plane region.
 4. Thebutton cell as claimed in claim 2, wherein the second portion of thefirst conductor is welded to the first of the cell cup plane region orthe cell top plane region via at least one weld bead or weld spotstarting from an outer side of the housing.
 5. The button cell asclaimed in claim 4, wherein the at least one weld bead or weld spotstarting from an outer side of the housing is at least one laser weldbead or laser weld spot.
 6. The button cell as claimed in claim 4,wherein the second portion of the second conductor is welded to thesecond of the cell cup plane region or the cell top plane region via atleast one second weld bead or second weld spot starting from an outerside of the housing.
 7. The button cell as claimed in claim 6, whereinthe at least one second weld bead or second weld spot starting from anouter side of the housing is at least one laser weld bead or laser weldspot.
 8. The button cell as claimed in claim 4, wherein the outer sideof the electrode winding is substantially cylindrical, wherein the bendconnecting the first portion of the first conductor to the secondstrip-shaped portion of the first conductor is disposed along a firstedge of the electrode winding, the first edge connecting the first endface of the electrode winding to the outer side of the electrodewinding, wherein the strip-shaped second portion of the first conductoris not folded between the bend of the first conductor and the at leastone weld bead or weld spot.
 9. The button cell as claimed in claim 2,wherein the electrode winding includes an open cavity extending alongthe axis, the open cavity having a first end and a second end extendingsubstantially parallel to cell cup plane region and the cell top planeregion, wherein the second portion of the first conductor is welded tothe first of the cell cup plane region or the cell top plane region inan area of the first of the cell cup plane region or the cell top planeregion that lies directly above or directly below the open cavity. 10.The button cell as claimed in claim 9, wherein the second portion of thesecond conductor is welded to the second of the cell cup plane region orthe cell top plane region in an area of the second of the cell cup planeregion or the cell top plane region that lies directly above or directlybelow the open cavity.
 11. The button cell as claimed in claim 9,wherein the open cavity of the electrode winding does not contain awinding core.
 12. The button cell as claimed in claim 9, wherein theopen cavity of the electrode winding includes a winding core.
 13. Thebutton cell as claimed in claim 1, wherein the first conductor and thesecond conductor, including the respective first portions, secondportions, and bends thereof, are metal foils having a thickness in arange of 5 μm to 100 μm.
 14. The button cell as claimed in claim 1,wherein the first conductor is an uncoated portion of the first currentcollector.
 15. The button cell as claimed in claim 14, wherein thesecond conductor is an uncoated portion of the second current collector.16. The button cell as claimed in claim 1, wherein the first portion ofthe first conductor is connected to the first current collector.
 17. Thebutton cell as claimed in claim 16, wherein the first portion of thefirst conductor is welded to the first current collector.
 18. The buttoncell as claimed in claim 16, wherein the first portion of the secondconductor is connected to the second current collector.
 19. The buttoncell as claimed in claim 18, wherein the first portion of the secondconductor is welded to the second current collector.
 20. The button cellas claimed in claim 19, wherein the first portion of the first conductoris welded to a first portion of the first current collector located in aradially peripheral region of the electrode winding, the first portionof the first current collector being a portion of the first currentcollector that is not coated with the first electrode material, whereinthe first portion of the second conductor is welded to a first portionof the second current collector, the first portion of the second currentcollector being a portion of the second current collector that is notcoated with the second electrode material, and wherein each respectivebend of the first conductor and the second conductor is a 90° bend. 21.The button cell as claimed in claim 20, wherein the first portion of thefirst conductor is disposed in the electrode winding radially outwardfrom the first portion of the first current collector, and wherein thefirst portion of the second conductor is disposed in the electrodewinding radially outward from the first portion of the second currentcollector.
 22. The button cell as claimed in claim 20, furthercomprising a first insulating strip attached to the first conductor anda second insulating strip attached to the second conductor, wherein thefirst insulating strip includes a first portion, a second portion, and abend connecting the first portion to the second portion, wherein thefirst portion of the first insulating strip is located radially inwardfrom the first portion of the first conductor, and the second portion ofthe first insulating strip is located axially inward from the secondportion of the first conductor, wherein the second insulating stripincludes a first portion, a second portion, and a bend connecting thefirst portion to the second portion, and wherein the first portion ofthe second insulating strip is located radially inward from the firstportion of the second conductor, and the second portion of the secondinsulating strip is located axially inward from the second portion ofthe second conductor.
 23. The button cell as claimed in claim 1, whereinthe first current collector and the second current collector aremetallic foils or meshes having a thickness in a range of 1 μm to 100μm.
 24. The button cell as claimed in claim 23, wherein the firstportion of the first conductor is welded to the first current collectorand the first portion of the second conductor is welded to the secondcurrent collector.
 25. The button cell as claimed in claim 1, furthercomprising: an electrically insulating seal separating the metal cellcup from the metal cell top; a first insulator positioned between thesecond portion of the first conductor and the first end side of theelectrode winding; and a second insulator positioned between the secondportion of the second conductor and the second end side of the electrodewinding.
 26. The button cell as claimed in claim 25, wherein the firstinsulator and the second insulator are thin plastic films.
 27. Thebutton cell as claimed in claim 26, further comprising an insulatingtape adhesively bonded to the first conductor.
 28. The button cell asclaimed in claim 27, further comprising a second insulating tapeadhesively bonded to the second conductor.
 29. The button cell asclaimed in claim 1, wherein the first electrode material includeslithium, wherein the first current collector is a first metallic foil ormesh comprising aluminum, and wherein the second current collector is asecond metallic foil or mesh comprising copper and/or nickel.
 30. Thebutton cell as claimed in claim 1, wherein the separator includesmultiple separator layers, and wherein the multi-layer assembly has oneof the following layer sequences: negative electrode/separatorlayer/positive electrode/separator layer, or positiveelectrode/separator layer/negative electrode/separator layer.